Merge pull request #699 from fartem/107_Binary_Tree_Level_Order_Traversal_II

2024-08-06 v. 6.4.0: added "107. Binary Tree Level Order Traversal II"

Author: fartem

README.md

@@ -505,3 +505,4 @@ Profile on LeetCode: [fartem](https://leetcode.com/fartem/).
 | 103. Binary Tree Zigzag Level Order Traversal                   | [Link](https://leetcode.com/problems/binary-tree-zigzag-level-order-traversal/)                   | [Link](./lib/medium/103_binary_tree_zigzag_level_order_traversal.rb)                   |
 | 105. Construct Binary Tree from Preorder and Inorder Traversal  | [Link](https://leetcode.com/problems/construct-binary-tree-from-preorder-and-inorder-traversal/)  | [Link](./lib/medium/105_construct_binary_tree_from_preorder_and_inorder_traversal.rb)  |
 | 106. Construct Binary Tree from Inorder and Postorder Traversal | [Link](https://leetcode.com/problems/construct-binary-tree-from-inorder-and-postorder-traversal/) | [Link](./lib/medium/106_construct_binary_tree_from_inorder_and_postorder_traversal.rb) |
+| 107. Binary Tree Level Order Traversal II                       | [Link](https://leetcode.com/problems/binary-tree-level-order-traversal-ii/)                       | [Link](./lib/medium/107_binary_tree_level_order_traversal_ii.rb)                       |

leetcode-ruby.gemspec

@@ -5,7 +5,7 @@ require 'English'
 ::Gem::Specification.new do |s|
   s.required_ruby_version = '>= 3.0'
   s.name = 'leetcode-ruby'
-  s.version = '6.3.9'
+  s.version = '6.4.0'
   s.license = 'MIT'
   s.files = ::Dir['lib/**/*.rb'] + %w[README.md]
   s.executable = 'leetcode-ruby'

lib/medium/107_binary_tree_level_order_traversal_ii.rb

@@ -0,0 +1,25 @@
+# frozen_string_literal: true
+
+# https://leetcode.com/problems/binary-tree-level-order-traversal-ii/
+# @param {TreeNode} root
+# @return {Integer[][]}
+def level_order_bottom(root)
+  return [] unless root
+
+  result = []
+  deq = [root]
+  until deq.empty?
+    level = []
+    size = deq.size
+    (0...size).reverse_each do |_i|
+      node = deq.shift
+      level << node.val
+      deq << node.left if node.left
+      deq << node.right if node.right
+    end
+
+    result << level
+  end
+
+  result.reverse
+end

test/medium/test_107_binary_tree_level_order_traversal_ii.rb

@@ -0,0 +1,35 @@
+# frozen_string_literal: true
+
+require_relative '../test_helper'
+require_relative '../../lib/common/binary_tree'
+require_relative '../../lib/medium/107_binary_tree_level_order_traversal_ii'
+require 'minitest/autorun'
+
+class BinaryTreeLevelOrderTraversalIITest < ::Minitest::Test
+  def test_default
+    assert_equal(
+      [[15, 7], [9, 20], [3]],
+      level_order_bottom(
+        ::TreeNode.new(
+          3,
+          ::TreeNode.new(9),
+          ::TreeNode.new(
+            20,
+            ::TreeNode.new(15),
+            ::TreeNode.new(7)
+          )
+        )
+      )
+    )
+    assert_equal(
+      [[1]],
+      level_order_bottom(
+        ::TreeNode.new(1)
+      )
+    )
+    assert_equal(
+      [],
+      level_order_bottom(nil)
+    )
+  end
+end